WordPress features and ‘pseudo’ cron function which loads at a certain interval when people visit your site. The Cron function is modeled after the linux/unix cron function which runs on most servers and check regularly for scheduled jobs to do.
The problem with the WordPress Cron is when nobody for a while visits your site. Or if you have a lot of heavy scheduled work to do this will slow down the user experience of your site.
There is a solution.